A lot of the best horror movies are films that blend horror with other genres, which I still categorize as horror. For example, Let the Right One In is really more of a coming of age drama along the lines of Fucking Amal, but that doesn't exclude it from being a horror film.

American Psycho falls into horror comedy (a la Tucker & Dale vs. Evil, Cheap Thrills) and is still a horror film whether you like it or not, chump.